Dark Water is a 2002 Japanese horror film directed by Hideo Nakata, who is better known as the director of Ringu and Ringu 2.

The plot involves a woman in the midst of an unpleasant divorce who moves to an eerie run-down apartment building with her young daughter. The ceiling of their apartment develops a leak, which progressively worsens, and the daughter finds an unfamiliar red bag while playing on the building's roof. The woman is disturbed to discover that the upstairs apartment that is the source of the leak was formerly the home of a young girl of similar age to her daughter who vanished more than a year before, whose body has never been found - and who owned a red bag.

Sensing something untoward, the woman disposes of the bag, however it reappears. Again the woman disposes of the bag, and again it reappears, establishing a pattern that becomes increasingly panicked, and driving the woman to the point of nervous hysteria, which in turn threatens her continued custody of her daughter. A sympathetic investigator teams with the woman to assist in uncovering the dark secret that lies at the heart of these events, and eventually they discover that the vanished child had in fact drowned in a rooftop water tank while trying to retreive her red bag, which had fallen inside. The tank then became the home to the child's malevolent spirit, spreading its evil via the building's plumbing.

The film's theme of a drowned innocent transmorgifying into a malevolent spiritual force is almost identical to that of Ringu - although the immediate cause of death in this case is accidental.

A U.S. remake of the film, directed by Walter Salles, is due out in mid-2005.